Hallo: I think this species is Ancistrosoma klugi, but with the next links (to see bellow) you will can study all the Ancistrosoma genus.
On another hand, 15 Ancistrosoma species are known (from Colombia, Ecuador, Peru, Venezuela, Trinidad and Tobago and a single species is recorded from Argentina (Katovich, 2008)) and the most useful work is Arrow (1913), but 4 species are not in his key!.
The type species is Ancistrosoma klugi Curtis, 1835 (by monotypy) and according to Katovich (2008): "The genus is characterized by its large size, elongate body, pronotum with the posterior margin bearing a single, narrow acuminate medial process; mesosternum medially interrupted by a broad triangular extension of the prosternum; 1st abdominal ventrite with posterior margin bearing a narrow, blunt acuminate process medially in males."
And please, you say to me when you downloaded all these papers, because I will delete some of them from the 4shared.
Best regards
Literature on Ancistrosoma (Macrodactylini):
Arrow 1913:
http://www.4shared.com/office/u2uKrvaf/Arrow_1913c_Synopsis_of_the_me.html
Ley, R. 1923:
http://gallica.bnf.fr/ark:/12148/bpt6k5458812s/f237
Salle 1886:
http://www.4shared.com/office/hgDS2wsE/Salle_1886_Monographie_du_genr.html
Salle 1886 plates:
http://www.4shared.com/office/i83ppnRe/Salle_1886_Plate_Monographie_d.html
Salle 1887:
http://www.4shared.com/office/lNOwa58a/Salle_1887_Espces_du_genre_Anc.html
Moser 1921:
http://www.archive.org/stream/stettinerentomol8284192123ento#page/n138/mode/1up
Arrow 1913:
http://www.archive.org/stream/ser8annalsmagazi12londuoft#page/424/mode/1up
Frey G. 1964:
http://www.4shared.com/office/xFOtAkCx/Frey_1964__Melolonthinae_del_M.html
Nonfried 1890:
http://www.4shared.com/office/xk5Rcosr/Nonfried_1890c_Ancistrosoma_ba.html
Erichson W.F. 1847:
http://www.archive.org/stream/archivfrnaturg1301berl#page/67/mode/1up
Latreille 1833- pág: 44.(como Melolontha rufipes):
http://www.4shared.com/office/4zCWmvZd/Latreille_1833_Scarabaeoidea.html
Blanchard 1850:
http://ia600301.us.archive.org/3/items/cataloguedelacol00mus/cataloguedelacol00mus.pdf
Curtis 1835:
http://www.archive.org/stream/transactionsofzo01zool#page/307/mode/1up
If do you want? I can send to you the next paper by E-amail: Katovich, K. 2008. A generic-level phylogenetic review of the Macrodactylini (Coleoptera:Scarabaeidae: Melolonthinae). Center for Systematic Entomology, Gainesville, Florida Insecta Mundi. 0023: 1- 78.